Tim Ring
  • Member for 5 years, 7 months
  • Last seen more than a month ago
  • Dublin, Ireland
What's a safe and easy way to desolder the CPU from C64?
Accepted answer
12 votes

The easiest way to desolder a dead chip is to cut the legs with your snips then remove each pin one at a time. Use a solder pump or solder braid to clean the holes. I would use an IC socket when ...

View answer
Faulty M1 line on the Z80A
4 votes

Looking at Spectrum schematics the M1 is not used at all! It is brought out to the edge connector though, so expansion packs may have used it. As regards faulty Z80s, I've never heard of any and I ...

View answer
Using DRAM as a camera sensor?
3 votes

Back around 1982, 1983 a friend of mine built a simple scanner using a 16k de-capped dram, probably a 4116. This was used on a Nascom 2 computer with a Nascom IMP dot matrix printer. The dram, along ...

View answer
EPROM software at conflicting addresses on Nascom computers
2 votes

Actually, a lot of code was supplied on tape, sometimes with relocators etc. Also the Z80 is not bad at relocatable code. The NAS-SYS monitors helped this relocatability substantially by clever use of ...

View answer
How does the Z80 determine which peripheral sent an interrupt?
2 votes

Have added this here as additional info to answers above (too big for comment)... The IEI / IEO are part of a daisy chain to determine interrupt priority. The signals are generated by the peripheral ...

View answer
Separate code and data address spaces on the Z80
2 votes

As answered the M1 is not used during full instruction fetch, just the first opcode byte. Note that the M1 has other purposes and shouldn't be messed with, especially if Z80 peripheral chips such as ...

View answer
When did the Z80 compatibles reach very high clock speed?
2 votes

I worked on Hypercom ICE credit card terminals in the noughties but the terminals date from the late nineties. They had dual Z80s running at approx 50mhz (one was used as the crypto engine). The ...

View answer
Better way to do Z80 "bank switch & call"?
1 votes

I have programmed on a device with paged flash memory (Hypercom Z80 based credit card terminal). It used a very simple scheme where the top 32K was paged (I think the terminal had 2mb flash). The ...

View answer
What stops an IO device from driving the databus longer than the CPU expects?
1 votes

The example timing diagram shown is for a complex situation where the CPU is acknowledging an interrupt and reading an interrupt vector (mode 2 interrupt operation). As noted before the IORQ line ...

View answer